Such a security document is known from German patent no. 16 96 245. According to the method described in this publication, a suitable carrier material, such as silk, cotton or plastics, is provided with a magnetic coating mixture and then embedded in the security document. If the security element is designed as a safeguarding thread, the magnetic band can additionally be coated on both sides with an opaque white coating slip. This prevents the dark ferromagnetic material from being detected without aid. It is a particular advantage of this safeguarding thread that it is almost impossible to detect visually in incident light (reflection) due to the high luminous reflectance on the white coating and the light scatter in the paper layer covering the safeguarding thread, but stands out very clearly from its surroundings as a dark coat in transmitted light. In addition the magnetic properties are clearly identifiable by machine.
However, it is increasingly proving to be disadvantageous that the magnetic properties can conceivably be imitated, at least to a limited extent, using commercially available magnetic tape materials (sound tapes, video tapes, etc.). Furthermore, most oxidic magnetic pigments are so dark that a complete white cover cannot be obtained with reasonable layer thicknesses. A safeguarding thread which is almost invisible in incident light is thus very difficult or even impossible to obtain with conventional means.
To make imitation more difficult, security documents are now frequently provided with additional security features which commercial magnetic tapes do not have. German patent no. 27 54 267 describes e.g. a security document having a security element with at least two different physical properties which can be checked independently of each other. One of the physical properties is fundamentally of magnetic nature. Magnetic materials with high coercive field strength and remanence are preferably used to protect magnetization codes from accidental demagnetization. A UV fluorescent material can be applied congruently to the magnetic patterns. Alternatively, an electrically conductive aluminum coating can be provided.
The production of such security elements is thus very elaborate and expensive since many individual phases of operation are necessary to apply the individual materials with the various physical properties successively and partly even in exact register.
The invention is therefore based on the problem of proposing a security element that is simple to produce, has both a light appearance and magnetic properties, and is still difficult to imitate due to its special magnetic properties.